|Alfred Binet psychometrics
Alfred Binet got the idea and collaborated with Théodore Simon to develop the first means of measuring intelligence. A sequence of simple tasks, progressively difficult, and calibrated to progressively older children, could determine whether a child was performing the same as his age group, the same as younger children, or the same as older children.
By focusing on tasks requiring judgment, attention, and reasoning, the Binet scale measured a child’s mental age, which for most children increases along with their physical age. An I.Q. based on the same kind of tests but expressed as a percentage of normal is thought to be fairly constant, even into adulthood. In adulthood, unless you are in the military, a measurement of your intelligence is much less important than what you produce.
Many skills, gifts, and qualities, and many contexts and relationships characterize a human being. If we could reduce the essential factors of success to a single number then we would call this a science. Heck! If we could describe a method then we could write a self-help book and sell millions of them.